Upload
randy-hardiansyah
View
243
Download
0
Embed Size (px)
Citation preview
8/16/2019 Ac Drives 01.ppt
1/16
The stator winding are supplied with balanced three-phase AC voltage,
which produce induced voltage in the rotor windings. It is possible toarrange the distribution of stator winding so that there is an effect of
multiple poles, producing several cycle of magnetomotive force (mmf) or
field around the air gap.
The speed of rotation of field is called the synchronous speed ωs , which
is defined by
p s
ω ω
2=
!s is syncronous speed "rad#sec$
%s is syncronous speed "rpm$
p is numbers of poles
! is the supply fre&uency "rad#sec$
f is the supply fre&uency "'$
%m is motor speed p
f
N s120
=
or
8/16/2019 Ac Drives 01.ppt
2/16
The rotor speed or motor speed is : )1( S sm −=ω ω
here * is slip, as defined as S
mS S ω
ω ω −= +r
S
mS
N
N N S
−=
The motor speed
8/16/2019 Ac Drives 01.ppt
3/16
Equivalent Circuit Of Induction Motor Equivalent Circuit Of Induction Motor
here
s is resistance per-phase of stator winding
r is resistance per-phase of rotor winding
s is leaage reactance per-phase of the
winding stator
s is leaage reactance per-phase of the
winding rotor
m is magnetiing reactance
m is Core losses as a reactance
8/16/2019 Ac Drives 01.ppt
4/16
Performance Characteristic of
Induction Motor
Stator copper loss : s scu s R I P 23=
'2')(3 r r cur R I P =Rotor copper loss :
m
s
m
mc
R
V
R
V
P
22
33 ≈=Core losses :
8/16/2019 Ac Drives 01.ppt
5/16
S
R I P r r g
'
2')(3=
)1()(3'
2' S S
R I P P P r r cur g d −=−=
)1( S P P g d −=
- Power developed on air ap !Power fropm stator to
rotor throuh air ap" :
Performance Characteristic of
Induction Motor
- Power developed #y motor :
or
- Torque of motor :
m
d d
P T ω
=
s
g
S
g P
S
S P
ω ω =
−−
=)1(
)1(or
m
d d
N P T π 2
60
=or
8/16/2019 Ac Drives 01.ppt
6/16
m s si I V P φ cos3=
g cu sc P P P ++=Input power of motor :
Performance Characteristic of
Induction Motor
load nod o P P P −=
g cu sc
load nod
i
o
P P P
P P
P
P
++−
==η
Output power of motor :
Efficiency :
8/16/2019 Ac Drives 01.ppt
7/16
)( cu sc g P P P +>>
load nod P P >>
S P
S P
P
P
g
g
g
d
−=
−
=≈ 1)1(
η
If
and
so, the efficiency can calculated as
Performance Characteristic of
Induction Motor
8/16/2019 Ac Drives 01.ppt
8/16
8/16/2019 Ac Drives 01.ppt
9/16
)(
)()(
''
''
r smr
s
r smr sm
i
X X X jS
R R
S
R R jX X X X
Z
++++
+++−=
Total Impedance of this circuit is
Performance Characteristic of
Induction Motor
m
The rotor current is
( ) 2
1
2'
2'
'
++
+
=
r sr
s
sr
X X S
R R
V I
8/16/2019 Ac Drives 01.ppt
10/16
( )
++
+
=2'
2'
2'3
r sr
s s
sr d
X X S
R RS
V RT
ω
Tor&ue 2 speed Characteristic
8/16/2019 Ac Drives 01.ppt
11/16
Three reion operation :
$% Motorin :
&% Reeneratin :
'% Pluin :
10 ≤≤ S
0
8/16/2019 Ac Drives 01.ppt
12/16
*tarting speed of motor is ωm 3 4 or * 3 5,
Performance Characteristic of
Induction Motor
*tarting tor&ue of motor is
( )
++
+
=2
'
2'
2'
3
r sr
s s
sr st
X X S
R R
V RT
ω
*lip for the ma6imum tor&ue *ma6 can be found by setting 0=dS T d d
*o, the slip on ma6imum tor&ue is
( ) ( )
[ ]2
12'2
'
max
r s s
r
X X R
RS
++±=
8/16/2019 Ac Drives 01.ppt
13/16
( )
+++=
2'2
2
max
2
3
r s s s s
s
X X R R
V T
ω
Performance Characteristic of
Induction Motor
Tor&ue ma6imum is
And the ma6imum regenerative tor&ue can be found as
( )
+++−= 2'2
2
max2
3
r s s s s
s
X X R R
V
T ω
here the slip of motor s 3 - *m
8/16/2019 Ac Drives 01.ppt
14/16
( )
++
+
=2
'
2'
2'3
r s
r
s s
sr d
X X S
R RS
V RT
ω Speed(Torque Characteristic :
( )2
'2'
+>>+
S
R R X X r sr s
( )2'2'3
r s s
sr d
X X S
V RT
+=
ω
( )2'2'
3
r s s
sr st
X X
V RT
+=ω
)or the hih Slip S% !startin"
So* the torque of motor is :
+nd startin torque !slip S,$" is :
8/16/2019 Ac Drives 01.ppt
15/16
( ) s
r
r s
RS
R X X >>
8/16/2019 Ac Drives 01.ppt
16/16
Stator -oltae Control
Controlling Induction 8otor *peed by
Ad9usting The *tator :oltage
( )
++
+
=2
'
2'
2'3
r sr
s s
sr d
X X S R RS
V RT
ω